Stop for antifriction screws



April 20, 1954 1 G. SPL-:TH

STOP FOR ANTIFRICTION SCREWS AND NUTS Filed Dec. 4, 1950 INVENTOR. LO-YD6'. SPETH A TTORNEY Patented Apr. 20, N1954 f STOP FOR ATIFRICTIONSCREWS AND NUTS Lloyd G. Speth, South Euclid, Ohio, assignor to TheCleveland Pneumatic Tool Company, Cleveland, Ohio, a corporation of OhioApplication December 4, 195.0, Serial No. 199,029

3 Claims. (Cl. 'Z4-459) This invention relates broadly to ananti-friction screw and nut mechanism of the ball-bearing type, but moreparticularly to a stop mechanism for limiting relative axial movement ofthe screw and nut.

One object of this invention is to provide a ball-bearing screw and nutassembly with a simple and eicient device limiting the axial movement ofone member relative to the other.

Another object of this invention is to provide such anti-friction screwand nut assembly with a stop preventing accidental disassembly of theparts.

Other objects of this invention not at this time more particularlyenumerated wil1 be clearly understood from the following` detaileddescription.

The invention is clearly illustrated in the accompanying drawing, inwhich:

Figure 1 is a longitudinal view, partly in section, of a ball-bearingscrew and nut assembly, embodying the invention.

Figure 2 is an enlarged end view, of the screw only, shown in Figure 1and looking in the direction of the arrows 2 2, while Figure 3 is asimilar view of the nut only.

Figure 4 is an enlarged end view of the screw and nut assembly, lookingin the direction of the arrows 2-2 in Figure 1, and showing the stop inoperative engagement.

Referring to the drawing, in which like symbols designate correspondingparts throughout the several views, I represents a sleeve or nut memberhaving a cylindrical bore extending therethrough, and in its surfacebeing provided with a spiral groove II. In cross section, this groove isslightly less than a senil-circle and with the normal surface of thebore, defines a spiral ridge I2.

Extending through the nut I0, there is a shaft or screw-member I3 of amaximum diameter slightly less than the inner diameter of the nut. Inits surface, the screw is provided with a complemental groove I4,corresponding in pitch to the pitch of the nut groove II, and of acrosssection also slightly less than a semi-circle. Like the groove I I,the groove I4 also defines with the normal surface of the screw, aspiral ridge I5. The turns of the spiral ridges I2 and I5 can be denedas coils, which as shown in Figure 1, extend in alternating relationshipwith the turns or coils of the grooves I I and I4.

When the grooves II and I4 are located to coincide, they will form aspiral channel of substantially circular cross-section, in which areinserted a plurality of anti-friction balls I6, which interconnect thenut and screw members, and

eifect the axial movement of one member relative to the other uponrotation of the former.

As usual in anti-friction screw and nut of the ball bearing type, thereis provided a ball recirculating device consisting of a by-pass passageI'I, leading from one end portion of the nut to the other.

Referring now more particularly to the invention, it will be understoodthat if the relative axial movement of the two main members, that is,the screw. I3 and nut Il), were not checked, either end of the screwgrooved portion could travel beyond the corresponding end of the nut,and cause the balls I6 to drop out of the'grooves II and III. Thiscondition would result in the complete disruption of the ball circuitand eiiect the disassembly of the device.

In the present construction, one end of the screw is provided with anintegral collar I8 engageable with the adjacent end I9 of the nut forlimiting axial movement of the screw toward the left in Figure 1.

To limit the axial movement of the screw I3 toward the right in Figure1, there is provided on the last -coil of the screw ridge I5, a radialprotuberance or lug 2E! of a radius slightly smaller than the radius ofthe nut groove II. Since the normal diameter of the screw is slightlysmaller than the normal inner diameter of the nut, it will be understoodthat before the insertion of the balls IB in the spiral channel I I-I4,the screw i3, except for the lug 20, would be free to slide axiallythrough the nut. With the lug 20 on the last coil of the screw ridge I5, the screw and nut can be assembled by simply screwing the lug 20through the groove I I of the nut.

After insertion of the balls I- in the spiral channel I I -IlI, thescrew ridges I5 will be placed in coinciding relationship with thecorresponding nut ridges I2, thereby preventing the radial lug 20 fromentering the nut groove I I and causing the lug, except for the cut awayportion hereinafter described, to enage the end face 2| of the nut I0,or more particularly the last coil of the nut spiral ridge I2.

In practice, it has been found that the engagement of the lug or stop2l! with the end face 2l of the nut I0 for checking further axialmovement of the screw, had the tendency to create a jamming action whichretarded or prevented the initial motion of the screw in the reverseddirection. To overcome this difficulty, the last coil of the nut spiralridge I2 adjacent the nut end 2I has a cut away portion 22, providing atits inner end a radial shoulder 23. This cut-away portion of the lastcoil of the nut ridge l2 enables the lug 20 to penetrate into the nutslightly beyond the nut end face 2|, and to contact the radial shoulder23 which is located within its path, to prevent further axial movementof the screw toward the right in Figure 1.

With the engaging surfaces of the lug 20 and shoulder 23 locatedradially of the nut and screw, the jamming action above referred to isentirely eliminated. The lug 20, which is preferably welded on the lastcoil of the screw ridge I5, is of a thickness equal to that of theridge, and of a lateral or peripheral extent sufiicient to provide astrong, non-deformable stop, capable of Vpositive engagement with theshoulder 23 for checking further movement of the screw in one directionirrespective of its rotation speed and the load to which it issubjected.

The details of structure and arrangement of parts shown and describedmay be variously changed and modified without departing from thespiritand scope of the invention.

I claim:

1. In combination, a screw member having a spiral groove and ridge invits surface, a nut member rhaving a complemental spiral groove andridge in its inner surface, a plurality of balls interengaged betweensaid two members in the grooves thereof for effecting axial movement ofone of said members relative to the other upon rotation of the former, alug extending radially from and peripherally on the spiral ridge of saidscrew member near one end thereof, a radial shoulder in the spiral ridgeof the nut member .near oneend thereof, the spiral ridge of said nutmember from said shoulder'to said lend thereof being cut away to enablesaid lug to penetrate into said nut member and engage said shoulder forlimiting said axial movement; in one direction.

2. In combination, a Ascrew member having a spiral groove and ridge inits surface, a nut member having a complemental Spiral groove and ridgein its inner surface, a plurality of balls interengaged between said twomembers in the grooves thereof for eecting axial movement of one of saidmembers relative to the other upon rotation of the former, a lugextending radially from the last coil of the spiral ridge of said screwmember, a radial shoulder in the last coil of the spiral ridge of saidnut nearest'to said lug, the end portion of said last coil up to saidshoulder being cut away to enable said lug to penetrate into said nutmember and engage said shoulder for limiting said axial movement in onedirection.

3'. In combination, a screw member having a spiral groove and ridge inits surface, a nut member having a complemental spiral groove and ridge`in its inner surface, a plurality of balls interengaged between saidtwo members in the grooves thereof for effecting axial movement of oneof said members relative t0 the other upon rotation of the former, a lugextending radially from the last coil of thev spiral ridge of said screwmember, the last coil ofthe spiral ridge of said nut member nearest tosaid lug having a cut-- away portion defining a radial shoulder locatedin the path of said lug and engaged thereby for limiting said axialmovement in one direction.

References Cited in the vile of this patent Germany May V11, 1920

